Automatic according to the working pressure of the systemOpening and closing, generally installed onClosed systemDevice orpipingTo protect the system security.
Chinese name
Pressure relief valve
Foreign name
decompression valves
Alias
Safety valve
Role
Ensure that the medium pressure in the equipment is below the setting
When the pressure in the equipment or pipeline exceeds the set pressure of the pressure relief valve, the pressure relief will be automatically opened to ensure that the medium pressure in the equipment and pipeline is below the set pressure, protect the equipment and pipeline and prevent accidents.[1]
working principle
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The pressure relief valve is composed of needle valve I, pressure gauge 2, main valve 3, pilot valve 4 and connecting pipe.[1]
It isHydraulic control valveOne of.The main valve is divided into upper and lower parts by the diaphragm. The lower chamber of the diaphragm is the water flow channel, and the upper chamber is the control room, which controls the opening and closing of the main valve disc.The pilot valve itself is a pressure relief valve, which also has a control room and a water flow channel. The opening and closing of the valve flap is controlled by the control room.Needle valve, namely throttle valve, controls the flow of water in the connecting pipe.[1]
During the operation of the fire water supply system, the water flow direction of the main pipe is from left to right, and one way of control water enters the pilot valve control room. When the water pressure is less than the set relief value, the thrust of the pilot valve spring is greater than the water pressure, and the pilot valve disc is closed.The other control water enters the upper chamber of the main valve through the throttle needle valve to generate a static pressure, and the pressure in the upper chamber is equal to that in the raw runner.Since the upper plane of the main valve disc is larger than the lower plane, the pressure of the upper chamber to the valve disc is greater than the push of the water to the valve disc in the main channel, making the main valve closed.If the water flow pressure of the main pipe rises and exceeds the set pressure relief value, the water flow pressure entering the conduit control room through the control pipe increases, and the water pressure is greater than the spring thrust. At this time, the pilot valve is opened, and the pressure on the main valve begins to release.Due to the restriction of the throttle valve, the water supply is insufficient, resulting in the reduction of the pressure in the upper chamber of the main valve and the marrow ice under the same valve.The flow thrust is greater than the upper chamber pressure, the valve disc rises, and the main valve opens for rapid pressure relief.Since the above process is completed instantaneously, the indoor fire water supply system will not cause harm in case of overpressure.[1]
If the water flow pressure of the main pipe continues to increase, the pilot valve opening amount will also increase so that the pressure difference between the upper chamber and the lower chamber of the main valve will be greater, the main valve opening amount will be greater, and the system pressure will be released faster.Conversely, if the water flow pressure of the main pipe decreases (such asIndoor fire hydrantWhen the number of nozzles used increases or the number of nozzles opened increases), the pressure in the pilot valve control room decreases accordingly, and the pilot valve opening amount decreases.The pressure in the upper chamber of the main valve increases, and the main valve disc closes after inquiry, so that the water flow pressure in the main pipeline is stable in the system design.[1]
classification
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Pressure relief valveThere are two main types of structures: spring type and lever type.[1]
Spring type refers to the valve disc andvalve seatThe seal of the depends on the force of the spring.
Lever type depends on the force of lever and heavy hammer.[1]
With the need of large capacity, there is another pulse typePressure relief valve, also known as pilot operatedPressure relief valve, byPressure relief valveAnd auxiliary valve.When the medium pressure in the pipeline exceeds the specified pressure value, the auxiliary valve is opened first, and the medium enters the main pipe along the conduitPressure relief valve, and set the mainPressure relief valveOpen to reduce the increased medium pressure.[1]
Operation method
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Pressure relief valveAdjustment of opening pressure[2]
1、Pressure relief valveBefore delivery, the opening pressure shall be adjusted one by one to the setting value required by the user.If the user proposes the working pressure level of the spring, it should be adjusted according to the lower limit of the pressure level.[2]
2. The user willPressure relief valveBefore installation on the protected equipment or before installation, readjustment must be made at the installation site to ensure thatPressure relief valveThe set pressure value of is in conformity with the requirements.[2]
3. Within the working pressure range of the spring indicated on the nameplate, the opening pressure can be adjusted by rotating the adjusting screw to change the compression amount of the spring.
4. Before rotating the adjusting screw, the valve inlet pressure should be reduced to less than 90% of the opening pressure to prevent the valve disc from being driven to rotate when rotating the adjusting screw, so as to damage the sealing surface.[2]
5. In order to ensure the accuracy of the opening pressure value, the medium conditions during adjustment, such as medium type, temperature, etc., should be as close as possible to the actual operating conditions.When the medium type changes, especially when the accumulation state of the medium is different (for example, from liquid phase to gas phase), the opening pressure often changes.When the operating temperature rises, the opening pressure generally decreases.Therefore, when it is adjusted at normal temperature and used for high temperature, the set pressure value at normal temperature should be slightly higher than the required opening pressure value.How high it is depends on the valve structure and material selection, which shall be based on the manufacturer's instructions.[2]
6. GeneralPressure relief valveFor the occasion of fixing the additional back pressure, when the opening pressure is adjusted after inspection (at this time, the back pressure is atmospheric pressure), the setting value shall be the required opening pressure minus the additional back pressure.[2]
characteristic
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1. Accurate and constant safe and stable pressure. Once overpressure occurs, the pressure relief valve can be fully opened to relieve pressure in time.[2]
2. The closing speed is adjustable to eliminate pressure fluctuation.[2]
3、the diaphragmThe transmission mechanism minimizes the operating hysteresis.
4. It can be installed at any position and can be repaired and inspected without changing the pressure setting value or removing it from the pipeline.[2]
matters needing attention
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It can automatically open when reaching the upper limit of the safety pressure to reduce the pressure to ensure safety. The most common is the pressure relief valve on the pressure cooker at home. It is a simple mechanical pressure relief valve, and the pressure relief valve of the heating and air-conditioning system is a water floating pressure relief valve. It is to release part of the pressure when the system pressure exceeds the design requirements,A valve that allows the system to work properly.[2]
1. The pressure relief valve can be installed horizontally or vertically, but attention should be paid to the inlet and outlet directions of the valve body during installation, and no mistakes should be made.Generally, one fire protectionWater supply systemOnly one pressure relief valve can be installed.[2]
2. If the drain outlet of the pressure relief valve is far away and the drain pipe is too long (>20m), the diameter of the drain pipe should be one gear larger than the specification of the pressure relief valve to prevent back pressure caused by poor discharge and ensure the stability of the pressure of the pipe network in front of the pressure relief valve.[2]
3. During the pressure test of the fire water supply system, if the system test pressure is higher than the nominal pressure of the selected relief valve l, the shut-off valve of the relief valve should be closed to avoid damage or failure of the relief valve.[2]
4. During the operation of the pressure relief valve, in case of failure and control failure, check whether the pipe is unblocked first.Recheck the valve on the control pipelineWater filterWhether it is blocked, whether the main valve and pilot valve membrane are broken, and whether the main valve and the viscous sealing gasket are damaged.[2]
